Walking and Mortality in Older Men

Abstract

Hakim et al. (Jan. 8 issue)¹ reported an association between regular walking and lower overall long-term mortality in retired nonsmoking men. The observed reduction in mortality was significant for cancer deaths but not for cardiovascular deaths. The lack of benefit in reducing cardiovascular mortality conflicts with previous studies from the Honolulu Heart Program, which reported that physical activity is associated with lower mortality from coronary heart disease, even after adjustment for smoking status,² and with a lower incidence of stroke in nonsmoking men.³ Furthermore, the association between walking and a lower risk of death from cancer is difficult to explain. The authors performed a precise adjustment of the effect of walking on mortality for cardiovascular risk factors. Although they attempted to adjust mortality reduction for disability and physical impairment, there was not an adequate control of confounding factors related to cancer or other causes. The relation between walking and lower mortality rates may not be causal. For instance, former smokers — apparently not excluded from the study — may have an impaired ability to walk due to chronic obstructive pulmonary disease, a condition associated with cancer⁴ and with an increased mortality risk.⁵ The hypothesis that walking a greater distance per day is a marker of less coexisting illness and lower cancer risk instead of a protector against overall and cancer-related mortality may have been too easily dismissed.